Online collaboration refers to two or more people collaborating or meeting remotely using computers to share documents, desktop applications, presentation slides, messages or multimedia data. In order to share information remotely, each collaborator's computer needs to communicate with the computer(s) of the other collaborators, either directly or indirectly. When computers are linked directly to each other, the communication model is termed peer-to-peer. Conversely, when one computer makes a request to the other computer indirectly via a server computer, the model is termed client-server (CS).
Online collaboration systems exist in both peer-to-peer and CS models. Peer-to-peer collaboration products such as Microsoft NetMeeting or AT&T Virtual Network Computing, are often limited to use by computers that are on the same network as they are not firewall friendly. A network firewall normally precludes an external computer from directly connecting to an internal computer. Moreover, peer-to-peer requires at least one of the peer computers to have a public IP address, an address publicly registered with the Network Information Center (NIC) that can be accessed by other computer over the Internet. Most corporate or home computers do not have public IP addresses, as such addresses are of limited supply. Peer-to-peer collaboration models are also limited in the number of participants they can accommodate, because each computer participating in the online collaboration session needs to be connected to all the others. The number of connections grows exponentially to the number of people collaborating.
Client-server online collaboration models require the installation, operation and maintenance of a proprietary application server. Such servers are responsible for routing and responding to client computer's requests. The client-server online collaboration model can scale to large number of users since each client computer only need to connect to the server. This model also addresses the firewall and IP problems as only the server needs to be outside of a firewall and has a public IP address. However, the proprietary application server used in such models requires an open channel with the collaboration participants during a session. They also require proprietary communication protocols that are computationally intensive. To this end, the server typically needs to be connected to a high-speed network and operated by IT specialists at high costs. Industry average of the annual cost of operating an enterprise server is at 3 to 6 times the cost of the server software. Many users end up using hosted services provided by application-service providers (ASP) and pay a monthly management fee.